For a charitable organization, corpus fund is of paramount importance.
Normally a corpus fund denotes a permanent fund kept for the basic expenditures needed for the administration and survival of the organization.
The corpus fund is generally not allowed to be utilized for the attainment of the purposes, but the interest/dividend accrued on such fund can be utilized or accumulated.
But for all practical purposes corpus fund is a permanently closed fund with no strings or restriction for future application attached.